Abstract: Digital seismic data recorded by 26 temporary stations from March to November in 2009 in the Three Gorges reservoir area were used to study the characteristics of anelastic attenuation in this region using the Atkinson's method and to obtain the site responses of 26 temporary stations using the Moya's method.Moreover,source parameters of 1020 earthquakes with magnitude bigger than 0.1 were calculated and used to study the scaling relations among them.Our results show that(1)The anelastic attenuation in Three Gorges reservoir is Q(f)=112.0f ^0.918,with a smaller value of Q₀ and bigger value of η.Site responses of most temporary stations are 1～10 times except a few stations.(2)Seismic moment M₀ increases with increasing magnitude M_L and their statistical relationship is LogM₀=1.07M_L+9.76.Relationship between stress drop and magnitude is consistent with the result gained by Nuttli that intraplate earthquake follows the ISD model,with a statistical relationship LogΔσ=0.66M_L-3.08.(3)Radiated seismic energy and apparent stress in Three Gorges reservoir all increase with increasing magnitude,indicating that a big earthquake is a more efficient radiator of seismic energy than a small earthquake.(4)Stress drops of reservoir induced earthquake are apparently smaller than that of tectonic earthquake with same magnitude,about 10 times smaller.These results may be due to the increase of pore pressure that leads to the occurrence of earthquake with a lower tectonic stress.

Key words: Three Gorges reservoir, source parameter, reservoir-induced earthquake, stress drop, apparent stress

摘要： 利用2009年3—11月三峡水库地区26个流动台站记录到的数字地震观测资料,首先采用Atk inson方法得到该地区地震波衰减特征,再用Moya方法得到26个台站的场地响应。在此基础上,精确测定得到了该地区1,020个M_L≥0.1地震的震源参数,开展了定标关系的研究。结果表明:1)三峡水库地区的非弹性衰减结果为Q(f)=112.0f^0.918,具有较小的Q₀值和较大的η值。除个别台站外,绝大部分流动台站的场地响应值位于1～10倍之间。2)地震矩M₀随震级M_L的增大而增大,两者之间存在较好的线性关系,统计关系为LogM₀=1.07M_L+9.76。应力降与地震大小之间的关系与Nuttli(1983)的板内地震为增加应力降(ISD)模型的结果比较吻合,统计关系为LogΔσ=0.66M_L-3.08。3)三峡水库地区地震辐射能量和地震视应力均随震级的增大而增大,后者意味着大地震是比小地震具更高效率的地震能量辐射体。4)与同震级的构造地震相比,水库地震的应力降值比前者明显偏低,约小10倍。这可能是由于水库蓄水造成地下介质孔隙压力增大,从而导致在一个比较低的构造应力情况下发生水库诱发地震。

关键词: 三峡水库, 震源参数, 水库诱发地震, 应力降, 视应力